FIX: Various watched words improvements

- Client-side censoring fixed for non-chrome browsers. (Regular expression rewritten to avoid lookback)
- Regex generation is now done on the server, to reduce repeated logic, and make it easier to extend in plugins
- Censor tests are moved to ruby, to ensure everything works end-to-end
- If "watched words regular expressions" is enabled, warn the admin when the generated regex is invalid

app/assets/javascripts/discourse/lib/text.js.es6

@@ -13,7 +13,7 @@ function getOpts(opts) {
     {
       getURL: Discourse.getURLWithCDN,
       currentUser: Discourse.__container__.lookup("current-user:main"),
-      censoredWords: site.censored_words,
+      censoredRegexp: site.censored_regexp,
       siteSettings,
       formatUsername
     },

app/assets/javascripts/discourse/models/topic.js.es6

@@ -97,7 +97,7 @@ const Topic = RestModel.extend({
   fancyTitle(title) {
     let fancyTitle = censor(
       emojiUnescape(title || ""),
-      Discourse.Site.currentProp("censored_words")
+      Discourse.Site.currentProp("censored_regexp")
     );
 
     if (Discourse.SiteSettings.support_mixed_text_direction) {

app/assets/javascripts/pretty-text/censored-words.js.es6

@@ -1,75 +1,19 @@
-function escapeRegexp(text) {
-  return text.replace(/[-/\\^$*+?.()|[\]{}]/g, "\\$&").replace(/\*/g, "S*");
-}
+export function censorFn(regexpString, replacementLetter) {
+  if (regexpString) {
+    let censorRegexp = new RegExp(regexpString, "ig");
+    replacementLetter = replacementLetter || "■";
 
-function createCensorRegexp(patterns) {
-  return new RegExp(`((?<!\\w)(?:${patterns.join("|")}))(?!\\w)`, "ig");
-}
-
-export function censorFn(
-  censoredWords,
-  replacementLetter,
-  watchedWordsRegularExpressions
-) {
-  let patterns = [];
-
-  replacementLetter = replacementLetter || "&#9632;";
-
-  if (censoredWords && censoredWords.length) {
-    patterns = censoredWords.split("|");
-    if (!watchedWordsRegularExpressions) {
-      patterns = patterns.map(t => `(${escapeRegexp(t)})`);
-    }
-  }
-
-  if (patterns.length) {
-    let censorRegexp;
-
-    try {
-      if (watchedWordsRegularExpressions) {
-        censorRegexp = new RegExp(
-          "((?:" + patterns.join("|") + "))(?![^\\(]*\\))",
-          "ig"
+    return function(text) {
+      text = text.replace(censorRegexp, (fullMatch, ...groupMatches) => {
+        const stringMatch = groupMatches.find(g => typeof g === "string");
+        return fullMatch.replace(
+          stringMatch,
+          new Array(stringMatch.length + 1).join(replacementLetter)
         );
-      } else {
-        censorRegexp = createCensorRegexp(patterns);
-      }
+      });
 
-      if (censorRegexp) {
-        return function(text) {
-          let original = text;
-
-          try {
-            let m = censorRegexp.exec(text);
-            const fourCharReplacement = new Array(5).join(replacementLetter);
-
-            while (m && m[0]) {
-              if (m[0].length > original.length) {
-                return original;
-              } // regex is dangerous
-              if (watchedWordsRegularExpressions) {
-                text = text.replace(censorRegexp, fourCharReplacement);
-              } else {
-                const replacement = new Array(m[0].length + 1).join(
-                  replacementLetter
-                );
-                text = text.replace(
-                  createCensorRegexp([escapeRegexp(m[0])]),
-                  replacement
-                );
-              }
-              m = censorRegexp.exec(text);
-            }
-
-            return text;
-          } catch (e) {
-            return original;
-          }
-        };
-      }
-    } catch (e) {
-      // fall through
-    }
+      return text;
+    };
   }
 
   return function(t) {
@@ -77,6 +21,6 @@ export function censorFn(
   };
 }
 
-export function censor(text, censoredWords, replacementLetter) {
-  return censorFn(censoredWords, replacementLetter)(text);
+export function censor(text, censoredRegexp, replacementLetter) {
+  return censorFn(censoredRegexp, replacementLetter)(text);
 }

app/assets/javascripts/pretty-text/engines/discourse-markdown/censored.js.es6

@@ -29,15 +29,11 @@ export function setup(helper) {
   });
 
   helper.registerPlugin(md => {
-    const words = md.options.discourse.censoredWords;
+    const censoredRegexp = md.options.discourse.censoredRegexp;
 
-    if (words && words.length > 0) {
+    if (censoredRegexp) {
       const replacement = String.fromCharCode(9632);
-      const censor = censorFn(
-        words,
-        replacement,
-        md.options.discourse.watchedWordsRegularExpressions
-      );
+      const censor = censorFn(censoredRegexp, replacement);
       md.core.ruler.push("censored", state => censorTree(state, censor));
     }
   });

app/assets/javascripts/pretty-text/pretty-text.js.es6

@@ -29,7 +29,7 @@ export function buildOptions(state) {
     lookupUploadUrls,
     previewing,
     linkify,
-    censoredWords,
+    censoredRegexp,
     disableEmojis
   } = state;
 
@@ -67,7 +67,7 @@ export function buildOptions(state) {
     formatUsername,
     emojiUnicodeReplacer,
     lookupUploadUrls,
-    censoredWords,
+    censoredRegexp,
     allowedHrefSchemes: siteSettings.allowed_href_schemes
       ? siteSettings.allowed_href_schemes.split("|")
       : null,